I'm programming for the iPhone and I'm wondering when to use the addSubview method of a view and when to present to use the modal view controller (presentModalViewController). What complicates this even more is if you are using a navigation controller (I'm not) and you can use the pushViewController method?
When would you use each and why?
Thanks.
-presentModalViewController and -pushViewController are two ways of going about the same thing: displaying a new view. Which you use depends on the user experience you're going for. They mean different things to the user, but are very similar in implementation.
-addSubview is completely different. It adds components to the current view. You should never use it to display an independent UI. -addSubview is most often used when programmatically creating the UI in -loadView, though it has many other uses.
Here's one way to look at it:
A sequence of view-controllers within single navigatoin controller represent a single workflow in user's head. If at some point you need to interrupt the current workflow and create a diverging workflow you create a modal dialog. If the new workflow only has one step you simply present corresponding controller, but if there are many steps you create a new navigation controller to string the steps together.
The visuals are different - with nav controller user's attention moves from left to right, while with modal dialog from top to bottom. Imagine that you are flipping a book (left-to-right) and at some point you move the book away from you and then pull another book from under the table and place it in front of you (top to bottom), and then start going through that another book (left-to-right). Then you close the whole second book and move back to first book where you left off.
The addSubview method is on a different abstraction plane - subviews are used to create the two experiences I described above. You can use subviews to create a different experience which would be on the same abstraction level. Couple more examples of the constructs on the same level are UIAlertView and UIActionSheet.
Related
Hy everybody
I am a newbie ios programmer and I'm facing many doubts when I must switch the pages of my app.
With the term "page" I mean a UIView that fills the whole screen with some widgets (buttons, textboxes. tables..)
As far as I have understood what I've read I should use an UIViewController to manage each of these pages
since each page should be a screen’s worth of content.
My App starts with a ViewScroller with many buttons and when the user clicks one of these it opens a new page.
The first page is the UIView connected to the RootController Of the Window.
So far to open the new pages I add a child controller to the RootController and it's view as a child of the view of the RootController:
RicLocaliController = [[RicercaLocaliViewController alloc] initWithNibName:#"RicercaLocaliViewController" bundle:nil];
[self addChildViewController:RicLocaliController];
[RicLocaliController didMoveToParentViewController:self];
[self.view addSubview:RicLocaliController.view];
RicLocaliController.view.frame = self.view.bounds;
When the user clicks the "Back" Button I remove the child controller and the child view.
Going down this road I would get a dynamic tree of Controllers with their Views.
So far I have not encountered problems and my app can go up to a third level in the tree and come back. Each page behaves correctly when orientation changes.
But I'm afraid that adding, for each subpage, a child controller and a child view could be not the right thing to do.
I'm afraid that if I nest a lot of pages when the orientation changes the app could respond slowly since also the superviews will do something to manage this event.
So what I wonder is if what I am doing is completely senseless, if I should use Navigation controllers or some other way to manage my page changes.
Unfortunately my boss is not giving me enough time to study well the subject and so I would like an advice to follow the best solution possibly using the most standard and less complex component offered by the framework instead of the newest features.
I read a lot of web pages on the subject but it seems to me that there are many ways to manage the navigation beetwen pages and this makes me confused.
I apologize for my bad english but i'm tired and English it's not my first language.
You HAVE to do some studying. You will spend more time clearing up all your problems later otherwise... but, here are some tips.
Using nested ViewControllers leads to all kinds of trouble so if you are short of time, skip that.
Think of each "Page" as one ViewController. A ViewController has a property called View but that is actually just the top view of a whole hierarchy of views. A view is the base class for any visual object, like labels, buttons etc. All views can have subviews, so you can add an image under a label etc. and do really wierd stuff if you want to. I am just saying this to free your mind about how you can use views.
Now, ViewControllers are supposed to hold to code to ONE view hierarchy. That view hierarchy is for that View Controller only.
When the user wants to navigate to another page, you have a few alternatives:
NavigationViewController - that should be used when the user wants to delve down into data, like opening a detailed view of an item in a list etc. The NavigationViewController gives you help with back buttons, proper animation etc. You "pop" a viewcontroller to go back one level. If the user click the back-button, this is automatic.
TabBarViewController - use that if you want a tab bar at the bottom of the screen. Each tab is connected to a ViewController, that has it's own view hierarchy.
PushModal - If you are in a ViewController and just needs to get some data from the user, which is not part of the normal navigation of the app, you can push a new ViewController modally. This is the way you interact with iOS built in ViewControllers. This is also a good way to get a value back from the view controller.
There you have it. Go learn more. :)
It sounds like, for what you are using, you should be using a navigation controller. This will automatically handle pushing views onto the stack and then popping them off again later. This will also automatically create a back button (it is customizable) in the navigation bar.
If you are using iOS 5 or 6, I highly recommend trying out "storyboards" in Interface Builder. Storyboards allow you to graphically represent transitions (called "segues") between different views.
On top of being easier to design and implement, another advantage is that, if in the future you want to change the design of your application, you don't have to trawl through all your code and manually update each view connection.
I'm trying to build an educational app that will have approximately 3-5 completely different pages/screens. Each screen contains one puzzle and each puzzle is independent of all the other puzzles (screens). Once the puzzle on the current screen is solved I'd like to transition to a new (randomly selected) screen. I would allow the same puzzle to be shown multiple times, however, if it had been displayed before it would need to be reset.
I've tried doing this using segues but that seems to require a UINavigationController which is not the experience I want to present (since it requires a predefined hierarchy of screens).
I assume the best way to do this is to have each screen as completely separate UIViewControllers, correct? I'm just not sure how to orchestrate the navigation/rendering between them.
I'd appreciate whatever best practices you know of. Thanks!
Well here is a possible option:
First of all if you want a menu outside of these puzzles have that as your root view controller in a UINavigationController.
Then create a launcher controller and add it to the navigation controller when appropriate. This will be a regular UIViewController except in this controller in the viewWillAppear method have it pick a random number 0-5 and run it through a switch and depending on the number push one of your 5 view controllers. Then when the puzzle is completed call popViewController on the navigation controller. Now when it pops back, viewWillAppear will be called again and randomly push another. Then if you want to go back to the main menu at any time just call popToRootViewControllerAnimated. This should do what you need. And to make it so it doesn't animate twice either only have the push animate or only the pop.
Rather than having different view controllers you can have a single controller. You can reload the view of the puzzle after completing the first. The logic you have applied for the first puzzle will be some what similar to the the others. So now only you need to handle different states of the puzzle.
For example: I have first view with puzzle 3x3 matrix, the next will be 4x4 matrix and the next will be 5x5 matrix. So this states needs to be handled through code in view controller.
I know that using cocos2d is a great way to build games and it allows different "scenes" where things are independent of each other or can communicate if you choose. Also with cocos2d there is a "director" that handles all of the scenes and can push scenes for you. If you are curious check out: www.cocos2d-iphone.org
I hope this helps :)
Well, I was build the app tested yesterday to play different music instrument. I use UIView to handle view for 3 of my instrument. The logic is simple. I put the navigation on UIButton and add a subview for each instrument. When the user touch the button, the selected view will be add to the front, and the last view will be release or temporary on the background.
Hope it will help you.
what is difference between view based and navigation based system in iphone . which one better to use and when?
if you have hierarchy of views, use navigation based else use view controller based.
You're talking about default templates that Xcode offers you to start your project with. It's not like they're different "systems" per se, they're just different starting points.
A view template is good if your app is one screen, or maybe a couple screens. Movement between those screens is up to you (and there are some pretty easy and good tools for animation screen changes, but you have to hook into those yourself).
A navigation template is good if you're going to be navigating a hierarchy of data, possibly with lists, sublists, detail screens, etc. Shifting between views is done with a call to UINavigationController, that handles all the transitioning business for you.
navigation based system is used if you want to use something like moving from main view to its inner view
like parent to child then subchild and so on...
While if you have no such hierarchy then you can use view based..
Navigation Based gives you a flexibility to reverse back to the view controller which you have already visited. like say for example you move 1->2->3->4->5 now if you want to go to 2 you can go easily. Navigation adds a top bar while view based is used if you dont want any kind of hierarchy..
hAPPY cODING...
I am trying to wrap my head around controllers in Cocoa Touch. The main problem is that I would like to have more than one controller “on screen” at once – I want to have a large view (with controller A) composed of smaller views controlled by their own controllers (say B). I’d like to have it this way because the division makes the code much cleaner. What’s bad is that the additional controllers (of type B) are not “first-class citizens” on the screen, for example they do not receive the autorotation queries and notifications. (And cannot easily display modal controllers, they have to send the presentModal… message to their parent controller.)
What is the difference between the A and B controllers from Cocoa viewpoint? Does the system keep some kind of pointer to the “frontmost controller”, a privileged one to which it sends notifications and such stuff? Why don’t the other controllers receive them, even though their views are on the screen? Is having multiple controllers “on screen” considered a hack? Or is it supported and I am just missing some point? Thank you.
More about the problem I am trying to solve: I am writing a simple photo browser. Photos are displayed in full screen, user can swipe left or right to change photos. The A controller takes care of the scrolling part and the B controllers take care of each photo itself.
Isolating B seemed like a good idea, since the photos are loaded from network and there is a lot that can happen, like the network might be down et cetera. In the B controller the code is fairly simple, since B only works with one particular photo. If I moved the code to the A controller, things would get messy.
The only thing I don’t like about the current solution is that I have to manually work around B not being a “first-class” controller. I have to pass some calls manually through A to B and when B wants to display a modal dialog, it has to send the presentModal… to A. Which is ugly.
There is now a first-class support for this scenario since iOS 5, it’s called controller containment.
swift controller containment
objc controller containment.
It's not closely related to the original question but important. Apple clearly states in View Controller Programming Guide that a view controller is responsible for controlling exactly one screen's content:
"Each custom view controller object you create is responsible for managing exactly one screen’s worth of content. The one-to-one correspondence between a view controller and a screen is a very important consideration in the design of your application. You should not use multiple custom view controllers to manage different portions of the same screen. Similarly, you should not use a single custom view controller object to manage multiple screens worth of content.
Note: If you want to divide a single screen into multiple areas and manage each one separately, use generic controller objects (custom objects descending from NSObject) instead of view controller objects to manage each subsection of the screen. Then use a single view controller object to manage the generic controller objects. The view controller coordinates the overall screen interactions but forwards messages as needed to the generic controller objects it manages."
However in iPad Programming Guide they also say that there may be container view controllers:
"A view controller is responsible for a single view. Most of the time, a view controller’s view is expected to fill the entire span of the application window. In some cases, though, a view controller may be embedded inside another view controller (known as a container view controller) and presented along with other content. Navigation and tab bar controllers are examples of container view controllers."
Up to my current knowledge I would not use sub-view controllers in a view controller but try to subclass NSObject and send messages to them from my main view controller.
Also check this thread:
MGSplitViewController discussion
First, and this is important, view controllers don't get "on screen" -- views do. Your "top level" controller can certainly pass along the kinds of messages you're describing to its "sub-view-controllers". In fact, this is how most apps work. Consider an app that has a tab bar, and where the views use navigation controllers. You actually have several view controllers "running" at the same time, each with its own view on screen at once -- your "root" view controller will be an instance (or subclass) of UITabBarController, which then has several nested UINavigationControllers, each which will display nested view controllers (like an instance or a subclass of UITableViewController).
You might want to read up a bit on how responder chains work. Consider a touch event. It will be generated for the view closest to the top of the stack, that can receive events, which is also underneath the tap. If that view can't handle it, it gets passed up the view hierarchy food chain until something deals with it (and then eats it).
As to the specifics of your question, on the whole, I'm not sure exactly what the strategy you describe is really doing to benefit you in terms of complexity. It depends on how exactly you're implementing things, but having separate view controllers for each little subview may require more bookkeeping code than just having one view controller that knows about all its sub-view components.
This is a pretty old question, but since I guess there are people who might face the same problem today I'd like to share my solution.
I was writing this application that had this one screen with a lot of information, pagination, controls etc. Since according to Apple's MVC documentation on the role of ViewControllers, you should not implement the logic in view itself, or access the data model directly from it, I had to choose between having a Massive ViewController with a few thousand lines of code which was both hard to maintain and debug(even with unit tests) or find a new way.
My solution was to use UIContainerView like below:
this way, you can implement each part's logic in it's own ViewController, and the parent view controller takes care of constraints and sizing of the views.
Note: This answer is just a guide to show the way, you can find a good and detailed explanation on how it works and how to implement it HERE
Actually you can make it work earlier than iOS 5, since most of us are targeting 4.x and 5.x at the same time. I've created a solution that works in both, and it works great, few apps in appstore use it :) Read my article about this or just download and use a simple class that I've created for this purpose.
What is the best approach to implement tabs that look like web applications on the iPhone, like the screenshot below (notice the "Checkin-Info-Friends" tabs)? These are not part of the UIKit standard library, but seems to be very common lately.
I've spent considerable time developing applications for the iPhone, but not developing controls like that one. What would be the best approach here:
create a new UIView for each tab content, and add the three subviews to the mainview straight away?
create new UIViews only when the user clicks on each of the tabs?
Put all the content in a UIScrollView, and just change the page as the user clicks on each tab?
Maybe there are open source controls for this out there? I couldn't find anything.
(source: foursquaregame.com)
My approach to a similar problem was to make all 4 (in my case) tab views, but respond to didReceiveMemoryWarning by releasing all but the current tab view. (Then, of course, you must make sure that you create the new view, if it doesn't exist, when the user chooses a new tab.)
I thought this was a good compromise - a speedy reaction to the user at first (and in my case memory footprint is at its lowest at this point in my app), and then a response to low memory to avoid being shot.
I think it best just to have three UIView* references to the subviews in the parent view or view controller, all initially null, then to have subroutine to hide the other two views if they are visible and either construct and show or just show the new view. Assuming no extraordinary memory requirements.
I think with such a small screen area load/unload concerns at the subview level are unlikely to be a concern, but if the parent views need to be loaded/unloaded, the subviews should all go (be both hidden and unloaded), and on reload, loadView should call the routine described in the last paragraph at startup.
If there is in fact a great deal of memory or resource use by any of the three subviews, then my advice is reversed and each of the subviews and/or any memory-intensive objects behind them should be not only hidden but unloaded whenever possible. I think with your use of Google maps there, a need to unload when hidden might apply to that.
Is this th right point to make? Is there some extra detail I'm missing?
You can have each tab be a real view controller with nib and everything. The only catch is that you must forward on the standard view controller calls you want to receive (viewWillAppear, etc) but it makes the coding much cleaner since you code just as you would for any other view (although for a smaller space).
You call each controllers "view" property to get out the view, which you add as a subview of a container view you have under the tabs.
If all three are table views, you might get away with using a single UITableViewController that changes contents based on the selected tab. Otherwise I second KHG's comment of using real view controllers to back up each of the subviews.
For the tabs themselves consider subclassing UISegmentedControl.